Effect of cadmium on bone tissue in growing animals

Adverse effects of cadmium on lymphoid organs, immune cells, and immunological responses

Humans and animals possess robust immune systems to safeguard against foreign pathogens. However, recent reports suggest a greater incidence of immunity breakdown due to exposure to environmental pollutants, with heavy metals emerging as potential candidates in such immuno-toxicological studies. While we have extensive data on the general toxicity resulting from exposure to heavy metals, comprehensive documentation of their role as immune disruptors remains scarce. Cd (Cadmium) exerts immunomodulation by interfering with immune organs and cells, leading to altered structure, physiology, and function, thereby inducing symptoms of immune deregulation, inflammation and/or autoimmunity. This review aims to summarize the link between Cd exposure and immune dysfunction, drawing from case studies on exposed human subjects, as well as research conducted on various model organisms and in-vitro culture systems.

Mechanisms of Phytoremediation by Resveratrol against Cadmium Toxicity

Cadmium (Cd) toxicity poses a significant threat to human health and the environment due to its widespread occurrence and persistence. In recent years, considerable attention has been directed towards exploring natural compounds with potential protective effects against Cd-induced toxicity. Among these compounds, resveratrol (RV) has emerged as a promising candidate, demonstrating a range of beneficial effects attributed to its antioxidant and anti-inflammatory properties. This literature review systematically evaluates the protective role of RV against Cd toxicity, considering the various mechanisms of action involved. A comprehensive analysis of both in vitro and in vivo studies is conducted to provide a comprehensive understanding of RV efficacy in mitigating Cd-induced damage. Additionally, this review highlights the importance of phytoremediation strategies in addressing Cd contamination, emphasizing the potential of RV in enhancing the efficiency of such remediation techniques. Through the integration of diverse research findings, this review underscores the therapeutic potential of RV in combating Cd toxicity and underscores the need for further investigation to elucidate its precise mechanisms of action and optimize its application in environmental and clinical settings.

Effects of selenium-cadmium co-enriched Cardamine hupingshanensis on bone damage in mice

Selenium (Se) and cadmium (Cd) usually co-existed in soils, especially in areas with Se-rich soils in China. The potential health consequences for the local populations consuming foods rich in Se and Cd are unknown. Cardamine hupingshanensis (HUP) is Se and Cd hyperaccumulator plant that could be an ideal natural product to assess the protective effects of endogenous Se against endogenous Cd-caused bone damage. Male C57BL/6 mice were fed 5.22 mg/kg cadmium chloride (CdCl2) (Cd 3.2 mg/kg body weight (BW)), or HUP solutions containing Cd 3.2 mg/kg BW and Se 0.15, 0.29 or 0.50 mg/kg BW (corresponding to the HUP0, HUP1 and HUP2 groups) interventions. Se-enriched HUP1 and HUP2 significantly decreased Cd-induced femur microstructure damage and regulated serum bone osteoclastic marker levels and osteogenesis-related genes. In addition, endogenous Se significantly decreased kidney fibroblast growth factor 23 (FGF23) protein expression and serum parathyroid hormone (PTH) levels, and raised serum calcitriol (1,25(OH)2D3). Furthermore, Se also regulated gut microbiota involved in skeletal metabolism disorder. In conclusion, endogenous Se, especially with higher doses (the HUP2 group), positively affects bone formation and resorption by mitigating the damaging effects of endogenous Cd via the modulation of renal FGF23 expression, circulating 1,25(OH)2D3 and PTH and gut microbiota composition.

Vitamin D Alleviates Cadmium-Induced Inhibition of Chicken Bone Marrow Stromal Cells' Osteogenic Differentiation In Vitro

Vitamin D is a lipid soluble vitamin that is mostly used to treat bone metabolism-related diseases. In this study, the effect of Cd toxicity in vitro on osteogenic differentiation derived from BMSCs and the alleviating effect of lα, 25-(OH)2D3 were investigated. Cell index in real time was monitored using a Real-time cell analyzer (RTCA) system. The activity of alkaline phosphatase (ALP), and the calcified nodules and the distribution of Runx2 protein were detected using ALP staining, alizarin red staining, and immunofluorescence, respectively. Furthermore, the mitochondrial membrane potential and the apoptotic rate of BMSCs, the mRNA levels of RUNX2 and type Ⅰ collagen alpha2 (COL1A2) genes, and the protein expression of Col1 and Runx2 were detected using flow cytometry, qRT-PCR and western blot, respectively. The proliferation of BMSCs and osteogenic differentiation were enhanced after treatment with different concentrations of lα, 25-(OH)2D3 compared with the control group. However, 5 μmol/L Cd inhibited the proliferation of BMSCs. In addition, 10 nmol/L lα,25-(OH)2D3 attenuated the toxicity and the apoptosis of BMSCs treated by Cd, and also promoted the osteogenic differentiation including the activity of ALP, and the protein expression of Col1 and Runx2. lα, 25-(OH)2D3 can alleviate cadmium-induced osteogenic toxicity in White Leghorn chickens in vitro.

Iron, Zinc, Copper, Cadmium, Mercury, and Bone Tissue

The paper presents the current understanding on the effects of five metals on bone tissue, namely iron, zinc, copper, cadmium, and mercury. Iron, zinc, and copper contribute significantly to human and animal metabolism when present in sufficient amounts, but their excess or shortage increases the risk of developing bone disorders. In contrast, cadmium and mercury serve no physiological purpose and their long-term accumulation damages the osteoarticular system. We discuss the methods of action and interactions between the discussed elements as well as the concentrations of each element in distinct bone structures.

Bone morphogenetic protein 4 is involved in cadmium-associated bone damage

Cadmium (Cd) is a well-characterized bone toxic agent and can induce bone damage via inhibiting osteogenic differentiation. Bone morphogenetic protein (BMP)/SMAD signaling pathway can mediate osteogenic differentiation, but the association between Cd and BMP/SMAD signaling pathway is yet to be illuminated. To understand what elements of BMPs and SMADs are affected by Cd to influence osteogenic differentiation and if BMPs can be the biomarkers of which Cd-induced osteoporosis, human bone marrow mesenchymal stem cells (hBMSCs) were treated with cadmium chloride (CdCl2) in vitro to detect the expression of BMPs and SMADs, and 134 subjects were enrolled to explore if the BMPs can be potential biomarkers of Cd-associated bone damage. Our results showed that Cd exposure significantly promoted the adipogenic differentiation of hBMSCs and inhibited its osteogenic differentiation by inhibiting the expression of BMP-2/4, SMAD4, and p-SMAD1/5/9 complex. And mediation analyses yielded that BMP-4 mediated 39.32% (95% confidence interval 7.47, 85.00) of the total association between the Cd and the risk of Cd-associated bone damage. Moreover, during differentiation, BMP-4 had the potential to enhance mineralization compared with CdCl2 only group. These results reveal that BMP-4 can be a diagnostic biomarker and therapeutic target for Cd-associated bone damage.

Effect of cadmium on Rho GTPases signal transduction during osteoclast differentiation

Osteoclasts are the key target cells for cadmium (Cd)-induced bone metabolism diseases, while Rho GTPases play an important role in osteoclast differentiation and bone resorption. To identify new therapeutic targets of Cd-induced bone diseases; we evaluated signal transduction through Rho GTPases during osteoclast differentiation under the influence of Cd. In osteoclastic precursor cells, 10 nM Cd induced pseudopodia stretching, promoted cell migration, upregulated the levels of Cdc42, and RhoQ mRNAs and downstream Rho-associated coiled-coil kinase 1 (ROCK1) and ROCK2 proteins, and downregulated the actin-related protein 2/3 (ARP2/3) levels. Cd at 2 and 5 μM shortened the pseudopodia, inhibited cell migration, and decreased ROCK1, ROCK2, and ARP2/3 protein levels; Cd at 5 μM also reduced the mRNA expression levels of Rac1, Rac2, and RhoU mRNAs and decreased the level of phosphorylated (p)-cofilin. In osteoclasts, 10 nM Cd induced the formation of sealing zones, slightly upregulated Cdc42 mRNA levels and ROCK2 and ARP2/3 protein levels and significantly reduced p-cofilin levels. Cd at 2 μM and 5 μM Cd blocked the fusion of precursor cells; and 5 μM Cd downregulated the expression levels of RhoB, Rac1, Rac3, and RhoU mRNAs, and ROCK1, p-cofilin and ARP2/3 protein levels, significantly. In vivo, Cd (at 5 or 25 mg/L) increased the levels of key proteins RhoA, Rac1/2/3, Cdc42, and RhoU and their mRNAs in bone marrow cells. In summary, the results suggested that Cd affected the differentiation process of osteoclast and altered the expression of several Rho GTPases, which might be crucial targets of Cd during the differentiation of osteoclasts.

Abnormal Bone Metabolism May Be a Primary Causative Factor of Keel Bone Fractures in Laying Hens

Simple Summary

Keel is an essential structural bone, providing anchorage for the attachment of large breast muscles in birds, allowing them to flap wings and provide proper ventilation for their lungs during flight. Previous studies reported that keel bone damage (especially fractures) negatively affects the welfare, health, production performance, eggshell quality, and mobility of laying hens contained in different housing systems. Furthermore, various factors affect keel bone damage, including nutrition, age, housing systems, and strains of laying hens. However, studies on the effects of abnormal bone metabolism and development on keel bone damage in laying hens are limited. Therefore, this study aimed to investigate the impacts of bone metabolism and development status on keel bone damage by determining the levels of serum bone turnover markers in laying hens. The results showed that laying hens with impaired keel bone had significantly altered levels of serum Ca and P metabolism-related and osteoblast and osteoclast activity-related markers compared to those in laying hens with normal keel bone. Thus, these results indicated that abnormal bone metabolism before keel bone damage reflected by varying levels of serum bone turnover markers might be a pivotal factor causing keel bone damage in laying hens. Our results also provide new insights into the occurrence of keel bone damage in laying hens.

Abstract

Keel bone damage negatively affects the welfare, production performance, egg quality, and mobility of laying hens. This study aimed to investigate whether abnormal bone metabolism causes keel bone damage in laying hens. Eighty Hy-line Brown laying hens were housed in eight furnished cages with 10 birds per cage and studied from 18 to 29 weeks of age (WOA). Accordingly, keel bone status was assessed at 18, 22, 25, and 29 WOA using the X-ray method, and the serum samples of laying hens with normal keel (NK), deviated keel (DK), and fractured keel (FK) that occurred at 29 WOA were collected across all the time-points. Subsequently, the serum samples were used to measure markers related to the metabolism of Ca and P and activities of osteoblast and osteoclast. The results showed that FK laying hens had lighter bodyweight than NK and DK birds throughout the trial (p < 0.05), while the keel bone length and weight were not different in NK, DK, and FK hens at 29 WOA (p > 0.05). Moreover, bone hematoxylin and eosin (H&E) staining and tartrate-resistant acid phosphatase (TRAP) staining indicated that damaged keel bone had evident pathological changes. In the FK hens, serum P level was reduced but serum 1,25-dihydroxy-vitamin D₃ (1,25-(OH)₂D₃) and 25-hydroxyvitamin D₃ (25-OHD₃) levels were elevated compared to NK hens (p < 0.05). Additionally, DK hens had higher levels of serum 1,25-(OH)₂D₃, parathyroid hormone (PTH) and calcitonin (CT), and lower level of serum 25-OHD₃ than the NK birds (p < 0.05). Furthermore, serum alkaline phosphatase (ALP), osteocalcin (OC), osteoprotegerin (OPG), TRAP, and corticosterone (CORT) levels were elevated in DK and FK hens compared to NK hens (p < 0.05). The levels of serum Ca, P, PTH, ALP, TRAP, OPG, OC, and CORT in laying hens fluctuated with the age of the birds. Generally, the results of this study indicate that keel bone damage, especially fractures, could be associated with abnormal bone metabolism in laying hens.

Chronic cadmium exposure at environmental-relevant level accelerates the development of hepatotoxicity to hepatocarcinogenesis

Cadmium (Cd) is an environmental heavy metal with long biological half-time and adverse health effects. The long-term toxicity of Cd at low levels remains to be elucidated. Here, we investigated the impact of dietary Cd intake at environmental doses in the full disease cycle from liver injury, fibrosis, inflammation to cancer progression in mouse models and in vitro. We found that chronic low-dose Cd exposure promoted the hepatotoxicity and hepato-pathogenesis in normal and CCl₄ mouse models. Cd enhanced liver injury and accelerated liver fibrosis, a key risk factor for cirrhosis and liver cancer, featured as up-regulation of fibrosis-related markers (TGF-β1, collagen-1, and TIMP1) and activation of hepatic stellate cells. Consistently, Cd increased the inflammation and the infiltration of macrophages and dendritic cells in liver. At late stage, the angiogenetic factors, VEGF and CD34, were elevated, indicating abnormal angiogenesis. At the end of treatment, Cd promoted CCl₄-induced liver cancer formation, including incidence, tumor number and size. These effects were more pronounced in male mice than that in females. The promoting-effects of Cd on fibrosis and angiogenesis were further validated in hepatic stellate cells and liver sinusoidal endothelial cells. PPAR and ERBB signaling pathways were identified as the potential pathways to promote the toxicity of chronic Cd exposure. These findings provide a better understanding about the long-term influence of environmental Cd spanning the entire precancerous lesions-to-cancer formation cycle.

The endocrine disruptor cadmium: a new player in the pathophysiology of metabolic diseases

Cadmium (Cd), a highly toxic heavy metal, is found in soil, environment and contaminated water and food. Moreover, Cd is used in various industrial activities, such as electroplating, batteries production, fertilizers, while an important non-occupational source is represented by cigarette smoking, as Cd deposits in tobacco leaves. Since many years it is clear a strong correlation between Cd body accumulation and incidence of many diseases. Indeed, acute exposure to Cd can cause inflammation and affect many organs such as kidneys and liver. Furthermore, the attention has focused on its activity as environmental pollutant and endocrine disruptor able to interfere with metabolic and energy balance of living beings. Both in vitro and in vivo experiments have demonstrated that the Cd-exposure is related to metabolic diseases such as obesity, diabetes and osteoporosis even if human studies are still controversial. Recent data show that Cd-exposure is associated with atherosclerosis, hypertension and endothelial damage that are responsible for cardiovascular diseases. Due to the large environmental diffusion of Cd, in this review, we summarize the current knowledge concerning the role of Cd in the incidence of metabolic and cardiovascular diseases.

Cadmium toxicity: A role in bone cell function and teeth development

Cadmium (Cd) is a widespread environmental contaminant that causes severe bone metabolism disease, such as osteoporosis, osteoarthritis, and osteomalacia. The present review aimed to explore the molecular mechanisms of Cd-induced bone injury starting from bone cell function and teeth development. Cd inhibits the differentiation of bone marrow mesenchymal stem cells (BMSCs) into osteoblasts, and directly causes BMSC apoptosis. In the case of osteoporosis, Cd mainly affects the activation of osteoclasts and promotes bone resorption. Cd-induces osteoblast injury and oxidative stress, which causes DNA damage, mitochondrial dysfunction, and endoplasmic reticulum stress, resulting in apoptosis. In addition, the development of osteoarthritis (OA) might be related to Cd-induced chondrocyte damage. The high expression of metallothionein (MT) might reduce Cd toxicity toward osteocytes. The toxicity of Cd toward teeth mainly focuses on enamel development and dental caries. Understanding the effect of Cd on bone cell function and teeth development could contribute to revealing the mechanisms of Cd-induced bone damage. This review explores Cd-induced bone disease from cellular and molecular levels, and provides new directions for removing this heavy metal from the environment.

Resveratrol protects MC3T3-E1 cells against cadmium-induced suppression of osteogenic differentiation by modulating the ERK1/2 and JNK pathways

Resveratrol (RES) is a natural polyphenolic compound with a broad range of physiological and pharmacological properties. Previous studies have shown that RES also plays an important role in protecting and promoting early bone metabolism and differentiation. The accumulation of cadmium (Cd), one of the world's most poisonous substances, can inhibit skeletal growth and bone maturation, thus causing osteoporosis. However, whether RES can prevent the Cd-induced inhibition of osteogenic differentiation remains unknown. In this study, we found that RES promoted the early maturity of osteoblastic MC3T3-E1 cells, as demonstrated by the significantly increased mRNA and protein expression of a range of differentiation markers, including alkaline phosphatase (ALP), collagen 1 (COL1), bone morphogenetic protein-2 (BMP-2), and runt-related transcription factor 2 (RUNX2). In contrast, we found that cadmium chloride (CdCl₂) inhibited the viability and osteogenic maturity of MC3T3-E1 cells. We also demonstrated that RES pretreatment for 30 min provided significant protection against Cd-induced apoptosis and attenuated the inhibition of osteogenic differentiation induced by Cd by modulating ERK1/2 and JNK signaling. In conclusion, our results indicate that RES is a potential femoral protectant that not only enhance the viability and early differentiation of osteoblasts, but also protect osteoblasts from cadmium damage.

Low-level cadmium exposure is associated with decreased cortical thickness, cortical area and trabecular bone volume fraction in elderly men: The MrOS Sweden study

It is well known that high-level exposure to cadmium can cause bone disease such as osteoporosis, osteomalacia and fractures. However, the effect of low-level exposure, as found in the general population (mainly derived from diet and smoking), has only been assessed recently. The aim of this study was to examine if cadmium exposure in the general Swedish population causes other bone changes than decreased areal bone mineral density as measured by traditional DXA technology, e.g. changes in microstructure and geometry, such as cortical thickness or area, cortical porosity and trabecular bone volume. The study population consisted of 444 men, aged 70-81 years at inclusion year 2002-2004, from the Swedish cohort of the Osteoporotic Fractures in Men Study (MrOS). Cadmium was analyzed in baseline urine samples (U-Cd). Different parameters of bone geometry and microstructure were measured at the distal tibia at follow-up in 2009, including examination with high-resolution peripheral quantitative computed tomography (HR-pQCT). Associations between bone parameters and U-Cd in tertiles were estimated in multivariable analyses, including potential confounding factors (age, smoking, BMI, and physical activity). We found significant associations between U-Cd and several bone geometry or microstructure parameters, with 9% lower cortical thickness (p = 0.03), 7% lower cortical area (p = 0.04), and 5% lower trabecular bone volume fraction (p = 0.02) in the third tertile of U-Cd, using the first tertile as the reference. Furthermore, significant negative associations were found between log-transformed U-Cd and cortical thickness, cortical area, trabecular number and trabecular bone volume fraction, and a significant positive association with trabecular separation. The results indicate that low-level Cd exposure in the general population has negative effects on both cortical and trabecular bone.

Long-Term Accumulation of Metals in the Skeleton as Related to Osteoporotic Derangements

The concentrations of metals in the environment are still not within the recommended limits as set by the regulatory authorities in various countries because of human activities. They can enter the food chain and bioaccumulate in soft and hard tissues/organs, often with a long half-life of the metal in the body. Metal exposure has a negative impact on bone health and may result in osteoporosis and increased fracture risk depending on concentration and duration of metal exposure and metal species. Bones are a long-term repository for lead and some other metals, and may approximately contain 90% of the total body burden in birds and mammals. The present review focuses on the most common metals found in contaminated areas (mercury, cadmium, lead, nickel, chromium, iron, and aluminum) and their effects on bone tissue, considering the possibility of the long-term bone accumulation, and also some differences that might exist between different age groups in the whole population.

Effects of cadmium on osteoblast cell line: Exportin 1 accumulation, p-JNK activation, DNA damage and cell apoptosis

Cadmium is an environmental metal pollutant that has been a focus of research in recent years, which is reported to cause bone disease; however, its skeletal toxicity and the mechanism involved are not yet fully known. Therefore, this study used MC3T3-E1 subclone 14 cells to determine the mechanism of cadmium toxicity on bone. Cadmium chloride (Cd) significantly reduced cell viability in a concentration-dependent manner. Exposure to Cd inhibited osteoblast-related proteins (Runx2, Col-1, STC2) and decreased alkaline phosphatase (ALP) activity. Cd caused Exportin-1 accumulation and induced DNA damage. Cd significantly down-regulated caspase 9 and induced cleaved-PARP, cleaved-caspase 3 protein level. Treatment with JNK inhibitor, SP600125, suppressed cadmium-induced elevation in the ratio of phosphorylation of JNK to JNK. Inhibition of caspase with pan-caspase inhibitor, Z-VAD-FMK, prevented MC3T3-E1 subclone 14 cells from cadmium-induced reduction of Runx2, STC2, caspase 9, and accumulation of cleaved PARP and cleaved caspase 3. Cd-induced cell survival enhanced by SP600125 but rescued by Z-VAD-FMK or KPT-335. These results suggest that cadmium cytotoxicity on bone involved exportin 1 accumulation, phosphorylation of JNK, induction of DNA damage and pro-apoptosis, which was induced by activation of caspase-dependent pathways.

Cadmium exposure triggers osteoporosis in duck via P2X7/PI3K/AKT-mediated osteoblast and osteoclast differentiation

Cadmium is a common environmental pollutant that accumulates in the bone and kidneys and causes severe health and social problems. However, the effects of Cd on the occurrence of osteoporosis and its mechanism of action in this process are unclear. To test whether Cd-induced osteoporosis is mediated via P2X7/PI3K/AKT signaling, duck bone marrow mesenchymal stem cells (BMSCs) and bone marrow macrophage cells (BMMs) were treated with Cd for 5 days, and duck embryos were treated with Cd_. Micro-CT analysis indicated that Cd-induced osteoporosis occurs in vivo, and histopathology and immunohistochemical analyses also revealed that Cd induced bone damage and the downregulation of osteogenic and bone resorption-related proteins. Cd exposure significantly inhibited the differentiation of BMSCs and BMMs into osteoblasts and osteoclasts in vitro, and promoted osteoblast and osteoclast apoptosis. Cd exposure significantly downregulated the P2X7/PI3K/AKT signaling pathway in vivo and in vitro, and inhibition of this signaling pathway significantly aggravated osteoblast and osteoclast differentiation. Cd exposure also upregulated the OPG/RANKL ratio in vivo and in vitro, further inhibiting osteoclast differentiation. These results demonstrate that Cd causes osteoporosis in duck by inhibiting P2X7/PI3K/AKT signaling and increasing the OPG/RANKL ratio. These results establish a previously unknown mechanism of Cd-induced osteoporosis.

Arsenic, cadmium, and selenium exposures and bone mineral density-related endpoints: The HORTEGA study

BACKGROUND AND OBJECTIVES

Experimental data suggest that trace elements, such as arsenic (As), cadmium (Cd), and selenium (Se) can influence the bone remodeling process. We evaluated the cross-sectional association between As, Cd, and Se biomarkers with bone mineral density (BMD) measured at the calcaneus, in a representative sample of a general population from Spain. As secondary analyses we evaluated the associations of interest in subgroups defined by well-established BMD determinants, and also conducted prospective analysis of osteoporosis-related incident bone fractures restricted to participants older than 50 years-old.

METHODS

In N = 1365 Hortega Study participants >20 years-old, urine As and Cd were measured by inductively coupled-plasma mass spectrometry (ICPMS); plasma Se was measured by atomic absorption spectrometry (AAS) with graphite furnace; and BMD at the calcaneus was measured using the Peripheral Instaneuous X-ray Imaging system (PIXI). As levels were corrected for arsenobetaine (Asb) to account for inorganic As exposure.

RESULTS

The median of total urine As, Asb-corrected urine As, urine Cd, and plasma Se was 61.3, 6.53 and 0.39 μg/g creatinine, and 84.9 μg/L, respectively. In cross-sectional analysis, urine As and Cd were not associated with reduced BMD (T-score < -1 SD). We observed a non-linear dose-response of Se and reduced BMD, showing an inverse association below ~105 μg/L, which became increasingly positive above ~105 μg/L. The evaluated subgroups did not show differential associations. In prospective analysis, while we also observed a U-shape dose-response of Se with the incidence of osteoporosis-related bone fractures, the positive association above ~105 μg/L was markedly stronger, compared to the cross-sectional analysis.

CONCLUSIONS

Our results support that Se, but not As and Cd, was associated to BMD-related disease. The association of Se and BMD-related disease was non-linear, including a strong positive association with osteoporosis-related bone fractures risk at the higher Se exposure range. Considering the substantial burden of bone loss in elderly populations, additional large prospective studies are needed to confirm the relevance of our findings to bone loss prevention in the population depending on Se exposure levels.

Association of Urinary and Blood Concentrations of Heavy Metals with Measures of Bone Mineral Density Loss: a Data Mining Approach with the Results from the National Health and Nutrition Examination Survey

Osteoporosis and its consequence of fragility fracture represent a major public health problem. Human exposure to heavy metals has received considerable attention over the last decades. However, little is known about the influence of co-exposure to multiple heavy metals on bone density. The present study aimed to examine the association between exposure to metals and bone mineral density (BMD) loss. Blood and urine concentrations of 20 chemical elements were selected from 3 cycles (2005-2010) NHANES (National Health and Nutrition Examination Survey), in which we included white women over 50 years of age and previously selected for BMD testing (N = 1892). The bone loss group was defined as participants having T-score < - 1.0, and the normal group was defined as participants having T-score ≥ - 1.0. We developed classification models based on support vector machines capable of determining which factors could best predict BMD loss. The model which included the five-best features-selected from the random forest were age, body mass index, urinary concentration of arsenic (As), cadmium (Cd), and tungsten (W), which have achieved high scores for accuracy (92.18%), sensitivity (90.50%), and specificity (93.35%). These data demonstrate the importance of these factors and metals to the classification since they alone were capable of generating a classification model with a high prediction of accuracy without requiring the other variables. In summary, our findings provide insight into the important, yet overlooked impact that arsenic, cadmium, and tungsten have on overall bone health.

The protective effects of simvastatin in Cadmium-Induced preosteoblast injury through Nox4

Cadmium (Cd) has a direct toxic effect on bones. Statins such as simvastatin have protective effects on various diseases, including on tissue injury. The current study revealed the efficacy of simvastatin on Cd-induced preosteoblast injury. Preosteoblast MC3T3-E1 cells were incubated with various doses of CdCl₂ for 12 h, 24 h and 48 h, and then the cell cytotoxicity was assessed using MTT assay and flow cytometry, respectively. The expression level of Nox4 was assessed by Western blot and qRT-PCR. The morphological appearance of MC3T3-E1 cells was observed under a microscope. Cells exposed to CdCl₂ (5 µM) were further treated by simvastatin at various doses, subsequently cell viability, apoptosis and the expression of Nox4 were measured. Furthermore, to confirm the protective effects of simvastatin on Cd-induced pre-osteoblast injury, functional rescue assays were performed after corresponding cell treatment by simvastatin (10^-8 M), CdCl₂ (5 µM), and overexpression of Nox4. Expressions of cell apoptosis-related markers were measured by Western blot and qRT-PCR. The results revealed that CdCl₂ caused MC3T3-E1 cell injury because the cell viability was decreased and the apoptosis was increased. Nox4 expression was up-regulated with the increase of CdCl₂ concentrations. Simvastatin increased the cell viability, relieved the cell apoptosis and Nox4 expression previously increased by CdCl₂. The effects of CdCl₂ on MC3T3-E1 cells and Nox4 expression could be attenuated by simvastatin, and promoted by Nox4 overexpression. The current study found that simvastatin protects Cd-induced preosteoblast injury via Nox4, thus, it can be used as a potential drug for treating cadmium-induced bone injury.

Cadmium induces apoptosis via generating reactive oxygen species to activate mitochondrial p53 pathway in primary rat osteoblasts

Cadmium (Cd), a heavy metal produced by various industries, contaminates the environment and seriously damages the skeletal system of humans and animals. Recent studies have reported that Cd can affect the viability of cells, including osteoblasts, both in vivo and in vitro. However, the mechanism of Cd-induced apoptosis remains unclear. In the present study, primary rat osteoblasts were used to investigate the Cd-induced apoptotic mechanism. We found that treatment with 2 and 5 μM Cd for 12 h decreased osteoblast viability and increased apoptosis. Furthermore, Cd increased the generation of reactive oxygen species (ROS), and, thus, DNA damage measured via p-H2AX. The level of the nuclear transcription factor p53 was significantly increased, which upregulated the expression of PUMA, Noxa, Bax, and mitochondrial cytochrome c, downregulated the expression of Bcl-2, and increased the level of cleaved caspase-3. However, pretreatment with the ROS scavenger N-acetyl-l-cysteine (NAC) or the p53 transcription specific inhibitor PFT-α suppressed Cd-induced apoptosis. Our results indicate that Cd can induce apoptosis in osteoblasts by increasing the generation of ROS and activating the mitochondrial p53 signaling pathway, and this mechanism requires the transcriptional activation of p53.

Adverse Impact of Heavy Metals on Bone Cells and Bone Metabolism Dependently and Independently through Anemia

Mounting evidence is revealing that heavy metals can incur disordered bone homeostasis, leading to the development of degenerative bone diseases, including osteoporosis, osteoarthritis, degenerative disk disease, and osteomalacia. Meanwhile, heavy metal-induced anemia has been found to be intertwined with degenerative bone diseases. However, the relationship and interplay among these adverse outcomes remain elusive. Thus, it is of importance to shed light on the modes of action (MOAs) and adverse outcome pathways (AOPs) responsible for degenerative bone diseases and anemia under exposure to heavy metals. In the current Review, the epidemiological and experimental findings are recapitulated to interrogate the contributions of heavy metals to degenerative bone disease development which may be attributable dependently and independently to anemia. A few likely mechanisms are postulated for anemia-independent degenerative bone diseases, including dysregulated osteogenesis and osteoblastogenesis, imbalanced bone formation and resorption, and disturbed homeostasis of essential trace elements. By contrast, remodeled bone microarchitecture, inhibited erythropoietin production, and disordered iron homeostasis are speculated to account for anemia-associated degenerative bone disorders upon heavy metal exposure. Together, this Review aims to elaborate available literature to fill in the knowledge gaps in understanding the detrimental effects of heavy metals on bone cells and bone homeostasis through different perspectives.

Effect of cadmium on osteoclast differentiation during bone injury in female mice

Cadmium (Cd) is a toxic heavy metal that represents an occupational hazard and environmental pollutant toxic heavy metal, which can cause osteoporosis following accumulation in the body. The purpose of this study was to investigate the effect of Cd on bone tissue osteoclast differentiation in vivo. Female BALB/c mice were randomly divided into three groups and given drinking water with various concentrations of Cd (0, 5, and 25 mg/L) for 16 weeks, after which the mice were sacrificed after collecting urine and blood. The level of Cd, calcium (Ca), phosphorus (P), trace elements, and some biochemical indicators were measured, and the bone was fixed in a 4% formaldehyde solution for histological observation. Bone marrow cells were isolated to determine the expression of osteoclast-associated mRNA and proteins. Cd was increased in the blood, urine, and bone in response to Cd in drinking water in a dose-dependent manner. The content of iron (Fe), manganese (Mn), and zinc (Zn) was significantly increased, whereas Ca and P were decreased in bone compared to the control group. Cd affected the histological structure of the bone, and induced the upregulation and downregulation of tartrate-resistant acid phosphatase 5b (TRACP-5b) and estradiol in the serum, respectively. Cd had no significant effect on the alkaline phosphatase activity in the serum. The expression of osteoclast marker proteins, including TRACP, cathepsin K, matrix metalloprotein 9, and carbonic anhydrases were all increased in the Cd-treated bone marrow cells. Cd significantly increased the expression of receptor activator of nuclear factor kappa B ligand (RANKL), but had lower effect on the expression of osteoprotegerin (OPG) in both bone marrow cells and bone tissue. Thus, Cd exposure destroyed the bone microstructure, promoted the formation of osteoclasts in the bone tissue, and accelerated bone resorption, in which the OPG/RANKL pathway may play an important role.

Melatonin protects bone against cadmium-induced toxicity via activation of Wnt/β-catenin signaling pathway

Among heavy metals, cadmium (Cd) is one of the most toxic for health due to it accumulation in several tissues including bone. Since melatonin (MLT) favors new bone formation through several pathways including Wnt/β-catenin, here we assessed whether MLT has a protective role against Cd induced toxicity in the rat bone tissue. Adult male Wistar rats receiving 50 mg CdCl₂/L and/or 3 mg/L MLT were used and were sacrificed 30 days after the treatment. Femurs and plasma were collected and analyzed by various biochemicals, molecular and histological investigation. The results showed that Cd exposure induced bone disorder characterized by histopathological alterations, a decreased alkaline phosphatase activity and plasmatic concentration of osteocalcin. Moreover, also the expression levels of some osteogenic-related genes (Runx2, Ocn and Alp) were down-regulated after Cd treatment. Since mechanistically Cd toxicity reduced the Kinase activity of GSK3β and protein levels of Wnt3a and β-catenin, we observed that MLT administration significantly ameliorated the toxic effects induced by the metal. Our findings provide clues about a potential protective effect of MLT against Cd-induced bone metabolism destruction and that the protection was partially mediated via the Wnt/β-catenin signaling pathway.

Dietary Cadmium Chloride Supplementation Impairs Renal Function and Bone Metabolism of Laying Hens

This study was conducted to evaluate the toxic effects of cadmium (Cd) on the kidney function and bone development in laying hens. A total of 480 Hy-line laying hens aged 38 weeks were randomly allocated into five treatments, each of which included six replicates of 16 birds. The concentrations of Cd in the diets of the five groups were 0.47, 7.58, 15.56, 30.55, and 60.67 mg/kg. Results showed that serum calcium (Ca) levels decreased significantly in the 60.67 mg Cd/kg diet group (p < 0.05). The activities of serum alkaline phosphatase (ALP) and bone ALP (BALP) decreased significantly in the 15.56, 30.55 and 60.67 mg Cd/kg diet groups (p < 0.05). The levels of parathyroid hormone (PTH) increased significantly in the 30.55 and 60.67 mg Cd/kg diet groups, and the estradiol (E2), 1,25-(OH)2-D3 and calcitonin (CT) decreased significantly with the increase of dietary Cd supplementation (p < 0.05). Histological results presented enlargements of renal tubules and tubular fibrosis in the kidney and decreased trabecular bone in the tibia. Tartrate-resistant acidic phosphatase (TRAP) staining results of tibia showed that osteoclast was significantly increased at the relatively high dose of dietary Cd (p < 0.05). In addition, the renal function indicators of blood urea nitrogen (BUN), urea acid (UA), and creatinine were significantly increased in Cd supplemented groups compared with the control group (p < 0.05). Low dose Cd exposure induced antioxidant defenses accompanying the increase in activities of catalase (CAT), glutathione peroxidase (GSH-Px), and the levels of glutathione (GSH) in renal tissue. At the same time, with the increased Cd levels, the activities of CAT, GSH-Px decreased significantly, and the level of malondialdehyde (MDA) increased significantly (p < 0.05). The activities of Na+/K+-ATPase and Ca2+/Mg2+-ATPase decreased significantly in the relatively high levels of dietary Cd (p < 0.05). These results suggest that Cd can damage renal function and induce disorders in bone metabolism of laying hens.

Alleviating Effect of α-Lipoic Acid and Magnesium on Cadmium-Induced Inflammatory Processes, Oxidative Stress and Bone Metabolism Disorders in Wistar Rats

Cadmium exposure contributes to internal organ dysfunction and the development of chronic diseases. The aim of the study was to assess the alleviating effect of α-lipoic acid and/or magnesium on cadmium-induced oxidative stress and disorders in bone metabolism, kidney and liver function, and hematological and biochemical parameters changes. Male rats were exposed to cadmium (30 mg Cd/kg of feed) for three months. Some animals exposed to Cd were supplemented with magnesium (150 mg Mg/kg of feed) and/or with α-lipoic acid (100 mg/kg body weight, four times a week). Cd intake inhibited body weight gain and lowered hemoglobin concentration, whereas it increased the activities of liver enzymes, as well as the level of oxidative stress, CTX-1 (C-terminal telopeptide of type I collagen, bone resorption marker), and CRP (C-reactive protein, marker of inflammation); it decreased vitamin D3, GSH (reduced glutathione), and the serum urea nitrogen/creatinine index. Mg and/or α-lipoic acid supplementation increased the antioxidant potential, and partially normalized the studied biochemical parameters. The obtained results show that both magnesium and α-lipoic acid decrease oxidative stress and the level of inflammatory marker, as well as normalize bone metabolism and liver and kidney function. Combined intake of α-lipoic acid and magnesium results in reinforcement of the protective effect; especially, it increases antioxidant defense.

The effect of cadmium exposition on the structure and mechanical properties of rat incisors

Alterations in the structure and mechanical properties of teeth in adult Wistar rats exposed to cadmium were investigated. Analyses were conducted on two sets of incisors from female and male specimens, that were intoxicated with cadmium (n = 12) or belonged to the control (n = 12). The cadmium group was administered with CdCl2 dissolved in drinking water with a dose of 4mg/kgbw for 10 weeks. The oral intake of cadmium by adult rats led to the range of structural changes in enamel morphology and its mechanical features. A significant increase of cadmium levels in the teeth in comparison to the control, a slight shift in the colour and reduction of pigmented enamel length, higher surface irregularity, a decrease of hydroxyapatite crystals size in the c-axis and simultaneous increase in pigmented enamel hardness were observed. The extent of these changes was sex-dependent and was more pronounced in males.

Early-Life Cadmium Exposure and Bone-Related Biomarkers: A Longitudinal Study in Children

BACKGROUND

Chronic cadmium exposure has been associated with osteotoxicity in adults, but little is known concerning its effects on early growth, which has been shown to be impaired by cadmium.

OBJECTIVES

Our objective was to assess the impact of early-life cadmium exposure on bone-related biomarkers and anthropometry at 9 y of age.

METHODS

For 504 children in a mother-child cohort in Bangladesh, cadmium exposure was assessed by concentrations in urine (U-Cd, long-term exposure) and erythrocytes (Ery-Cd, ongoing exposure) at 9 and 4.5 y of age, and in their mothers during pregnancy. Biomarkers of bone remodeling [urinary deoxypyridinoline (DPD), urinary calcium, plasma parathyroid hormone, osteocalcin, vitamin D3, insulin-like growth factor (IGF) 1, IGF binding protein 3, thyroid stimulating hormone] were measured at 9 y of age.

RESULTS

In multivariable-adjusted linear models, a doubling of concurrent U-Cd was associated with a mean increase in osteocalcin of [Formula: see text] (95% CI: 0.042, 5.9) and in urinary DPD of [Formula: see text] (95% CI: 12, 32). In a combined exposure model, a doubling of maternal Ery-Cd was associated with a mean increase in urinary DPD of [Formula: see text] (95% CI: [Formula: see text], 30). Stratifying the osteocalcin model by gender ([Formula: see text] 0.001), a doubling of concurrent U-Cd was associated with a mean decrease in osteocalcin of [Formula: see text] (95% CI: [Formula: see text], [Formula: see text]) in boys and a mean increase of [Formula: see text] (95% CI: 5.4, 13) in girls. The same pattern was seen with U-Cd at 4.5 y of age ([Formula: see text] 0.016). Children's U-Cd and Ery-Cd, concurrent and at 4.5 y of age, were inversely associated with vitamin D3.

CONCLUSIONS

Childhood cadmium exposure was associated with several bone-related biomarkers and some of the associations differed by gender. https://doi.org/10.1289/EHP3655.

Anti-Osteogenic Activity of Cadmium in Zebrafish

Among the many anthropogenic chemicals that end up in the aquatic ecosystem, heavy metals, in particular cadmium, are hazardous compounds that have been shown to affect developmental, reproductive, hepatic, hematological, and immunological functions in teleost fish. There is also evidence that cadmium disturbs bone formation and skeletal development, but data is scarce. In this work, zebrafish was used to further characterize the anti-osteogenic/osteotoxic effects of cadmium and gain insights into underlying mechanisms. Upon exposure to cadmium, a reduction of the opercular bone growth was observed in 6-days post-fertilization (dpf) larvae and an increase in the incidence of skeletal deformities was evidenced in 20-dpf post-larvae. The extent and stiffness of newly formed bone was also affected in adult zebrafish exposed to cadmium while regenerating their caudal fin. A pathway reporter assay revealed a possible role of the MTF-1 and cAMP/PKA signaling pathways in mechanisms of cadmium osteotoxicity, while the expression of genes involved in osteoblast differentiation and matrix production was strongly reduced in cadmium-exposed post-larvae. This work not only confirmed cadmium anti-osteogenic activity and identified targeted pathways and genes, but it also suggested that cadmium may affect biomechanical properties of bone.

A Review of Metal Exposure and Its Effects on Bone Health

The presence of metals in the environment is a matter of concern, since human activities are the major cause of pollution and metals can enter the food chain and bioaccumulate in hard and soft tissues/organs, which results in a long half-life of the metal in the body. Metal intoxication has a negative impact on human health and can alter different systems depending on metal type and concentration and duration of metal exposure. The present review focuses on the most common metals found in contaminated areas (cadmium, zinc, copper, nickel, mercury, chromium, lead, aluminum, titanium, and iron, as well as metalloid arsenic) and their effects on bone tissue. Both the lack and excess of these metals in the body can alter bone dynamics. Long term exposure and short exposure to high concentrations induce an imbalance in the bone remodeling process, altering both formation and resorption and leading to the development of different bone pathologies.

AKT inhibition-mediated dephosphorylation of TFE3 promotes overactive autophagy independent of MTORC1 in cadmium-exposed bone mesenchymal stem cells

Cadmium (Cd) is a toxic metal that is widely found in numerous environmental matrices and induces serious adverse effects in various organs and tissues. Bone tissue seems to be a crucial target of Cd contamination. Macroautophagy/autophagy has been proposed to play a pivotal role in Cd-mediated bone toxicity. However, the mechanisms that underlie Cd-induced autophagy are not yet completely understood. We demonstrated that Cd treatment increased autophagic flux and inhibition of the autophagic process using Atg7 gene silencing blocked the Cd-induced mesenchymal stem cell death. Mechanistically, Cd activated nuclear translocation of TFE3 but not that of TFEB or MITF, which contributed to the expression of autophagy-related genes and lysosomal biogenesis. Specifically, Cd decreased expression of phospho-AKT (Ser473). The reduction in AKT activity led to dephosphorylation of cytosolic TFE3 at Ser565 and promoted TFE3 nuclear translocation independently of MTORC1. Notably, Cd treatment increased the activity of PPP3/calcineurin, and pharmacological inhibition of PPP3/calcineurin with FK506 suppressed AKT dephosphorylation and TFE3 activity. These results suggest that PPP3/calcineurin negatively regulates AKT phosphorylation and is involved in Cd-induced TFE3-dependent autophagy. Modulation of the PPP3/calcineurin-AKT-TFE3 autophagic-lysosomal machinery may offer novel therapeutic approaches for the treatment of Cd-induced bone damage. Abbreviations: ACTB: actin: beta; AKT: thymoma viral proto-oncogene; AMPK: AMP-activated protein kinase; ATG: autophagy related; Baf A1: bafilomycin A₁; Cd: cadmium; FOXO3: forkhead box O3; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MITF: melanogenesis associated transcription factor; MSC: mesenchymal stem sell; MTORC1: mechanistic target of rapamycin kinase complex 1; RPS6KB1: ribosomal protein S6 kinase: polypeptide 1; SGK1: serum/glucocorticoid regulated kinase 1; SQSTM1/p62: sequestosome 1;TFE3: transcription factor E3; TFEB: transcription factor EB; TFEC: transcription factor EC.

Effect of Cd and Pb Pollutions on Physiological Growth: Wavelet Neural Network (WNN) as a New Approach on Age Determination of Coenobita scaevola

Environmental pollution of aquatic ecosystems leads to an interference in several fundamental biochemical and physiological functions. In this study the interference of Cd and Pb pollutions on the physiological growth and subsequently on the age determination was investigated. The hermit crab, Coenobita scaevola (C.s) was selected as a bioaccumulator in this study. The direct and indirect age determination methods were carried out using annual band counts and carapace length, respectively. The results showed that, there was very low correlation (R² < 0.5) between direct and indirect age determination. Wavelet Neural Network (WNN) was applied to take into account the environmental effects such as the accumulation of Cd and Pb elements in the C.s' tissues. It was observed that WNN successfully enhanced the growth rate model and estimated the C.s' age (R² > 0.95). In addition, it was concluded that the environmental pollution had interaction with the growth physiology such as weight and length.

Biochemical and transcriptional analyses of cadmium-induced mitochondrial dysfunction and oxidative stress in human osteoblasts

Cadmium (Cd) accumulation is known to occur predominantly in kidney and liver; however, low-level long-term exposure to Cd may also result in bone damage. Few studies have addressed Cd-induced toxicity in osteoblasts, particularly upon cell mitochondrial energy processing and putative associations with oxidative stress in bone. To assess the influence of Cd treatment on mitochondrial function and oxidative status in osteoblast cells, human MG-63 cells were treated with Cd (up to 65 μM) for 24 or 48 h. Intracellular reactive oxygen species (ROS), lipid and protein oxidation and antioxidant defense mechanisms such as total antioxidant activity (TAA) and gene expression of antioxidant enzymes were analyzed. In addition, Cd-induced effects on mitochondrial function were assessed by analyzing the activity of enzymes involved in mitochondrial respiration, membrane potential (ΔΨm), mitochondrial morphology and adenylate energy charge. Treatment with Cd increased oxidative stress, concomitantly with lipid and protein oxidation. Real-time polymerase chain reaction (qRT-PCR) analyses of antioxidant genes catalase (CAT), glutathione peroxidase 1 (GPX1), glutathione S-reductase (GSR), and superoxide dismutase (SOD1 and SOD2) exhibited a trend toward decrease in transcripts in Cd-stressed cells, particularly a downregulation of GSR. Longer treatment with Cd (48 h) resulted in energy charge states significantly below those commonly observed in living cells. Mitochondrial function was affected by ΔΨm reduction. Inhibition of mitochondrial respiratory chain enzymes and citrate synthase also occurred following Cd treatment. In conclusion, Cd induced mitochondrial dysfunction which appeared to be associated with oxidative stress in human osteoblasts.

Selenium supplementation can protect from enhanced risk of keel bone damage in laying hens exposed to cadmium

The aim of this study was to investigate whether selenium (Se) supplementation can provide protection from an enhanced risk of keel bone damage (KBD) in laying hens due to the cadmium (Cd) toxicity associated with sub-chronic exposure.